Medical catheters have been used to access locations within a patient without invasive surgery. The catheter may be introduced into a body passageway at locations where the passageway is near the skin. The catheter can then be advanced to an area of interest. Often, the ability to control the exact position and orientation of the tip of a catheter largely determines the usefulness of the catheter.
One known application for medical catheters is for the recording and mapping of endocardial signals, for example, to identify the focus or foci of a dysrhythmia or to ablate endo- or myocardial tissue. The success and advancement of current techniques has been dependent upon the development and use of more precise techniques for locating arrhythmogenic sites. Further, the operator (e.g., electrophysiologist) has had to compromise between placing the catheter in the place of greatest clinical interest verses placing the catheter in areas which are anatomically accessible.
To assist positioning a catheter at a desired location within a body, pre-shaped catheters have been constructed. Known catheters have been shaped to specifically access a particular site within the body. For example, U.S. Pat. No. 4,882,777 of Narula discloses a catheter having a complex multi-planar curvature which automatically positions the distal end of the catheter at a desired internal location. This particular catheter is designed to traverse the inferior vena cava through the tricuspid valve and into the right ventricle from the right atrium. Another catheter containing pre-shaped sections is disclosed in U.S. Pat. No. 5,423,772 of Lurie et al. That catheter has a distal portion containing a first longitudinal curve of a radius between 7.0 cm and 11.0 cm and a second longitudinal curve of between 0.5 cm and 2.0 cm. Both of these longitudinal curves are curved in the same direction. Other examples of the preshaped catheters are shown in U.S. Pat. Nos. 3,485,234 and 3,503,385, both of Stevens, U.S. Pat. No. 3,729,008 of Berkovits, and U.S. Pat. No. 4,860,769 of Forgerty, each of which is hereby incorporated by reference as if set forth in their entireties herein.
Steerable catheters have also been used to direct the catheter to a desired location, and properly orient or position the catheter at the desired location. For example, U.S. Pat. No. 5,327,905 of Avitall discloses a pre-formed catheter section designed to be steered into a position on either the atrial or ventricular side of the A-V ring. Other steerable catheter designs are disclosed in, for example, U.S. Pat. No. Re. 34,502 of Webster, Jr. and U.S. Pat. No. 4,920,980 is of Jackowski.
The object of this invention, therefore, is to provide a catheter which is capable of being properly positioned against the wall of the right atrium.
A further object of the invention is to provide a catheter which may be nested within the tricuspid valve without prolapsing through the valve as the catheter is rotated during use.